This invention relates to oxygen-fuel burners in general, and more specifically to burners utilizing oxygen, as opposed to air, as the oxidizing agent for the fuel; and a liquid fuel such as oil, or a dispersion of solid fuel in a fluid medium, which necessitates the atomization of the fuel so as to promote complete efficient combustion of the fuel when mixed with the oxidant, hereinafter referred to as oxy-oil burners. The oxy-oil burners of the present invention are not liquid cooled, but have a wide range of flow rates while maintaining safe burner tip temperatures.
The prior art is replete with burner assemblies of different configurations, however, most of such burners relate to oxy-gas or air-oil operations rather than the unique concerns of the oxy-oil burner of the present invention.
U.S. Pat. No. 3,809,525 relates to a flat-flame burner utilizing an air-oil combustion mixture, wherein the burner tip is provided with helicoid passages for atomizing fuel oil droplets and mixing with eddying secondary air escaping adjacent the tip.
U.S. Pat. No. 4,230,449 discloses a low pressure air-oil burner capable of generating a relatively long narrow flame. An atomizer, having a venturi and a swirl plate to atomize a fuel oil, is positioned within a primary air chamber so as to provide a distribution which is not rotationally symetric about the chamber axis, and therefore is not subject to stability and vibration problems.
U.S Pat. No. 4,541,796 relates to an oxygen-oil aspirator burner and discusses the advantages and disadvantages of oxygen replacing air for combustion. The principal advantages noted are an increase in the maximum achievable firing rate, a decrease in fuel consumption and a decrease in pollution problems relating to entrainment of particles, as well as a decrease in the nitrogen portion in both the oxidant and flue gas. However, the noted disadvantages included a lower gas momentum in the furnace and higher flame temperatures which produce local hot spots and increase nitrogen oxide (NO.sub.x) emissions. In order to overcome the disadvantages and utilize the advantages of oxygen, the patent discloses the use of oxygen jets introduced at a velocity sufficient to cause aspiration of furnace gases into the oxidant jets before the latter mix with the fuel jet, in amounts sufficient to lower flame temperature.
U.S. Pat. No. 4,690,635 relates to a high temperature oxy-gas burner assembly wherein the gas conduit tip has a frusto-conical portion forming a knife edge for briefly delaying combustion, which tip is surrounded by a plurality of oxygen emitting holes disposed in a circular array or an annular shaped oxygen emitting orifice, or both.
U.S. Pat. No. 4,726,760 relates to an air-oil burner wherein the oil is formed into minute fuel particles in the form of a spray cone, by being discharged through a central port which is defined by a continuous knife edge. The spray cone is bounded by an external rotating flow of air.
In order to overcome the problems and complexities with the above-noted burner assemblies of the prior art, it is an object of the present invention to provide an oxy-oil burner having a wide range of flow rates and which maintains an acceptable cool body tip temperature, even at relatively low flow rates and even when oxygen is used as the atomizing fluid, without the use of liquid cooling.
Operationally, the improved structure of the present oxy-oil burner permits the previously unthinkable use of commercially pure oxygen or oxygen enriched gases as the atomizing fluid, by providing a boundary layer annulus which precludes fuel "cracking" in the atomizing chamber and prevents the collecting of minute oil particles adjacent the burner tip. Further, by utilizing carbon dioxide as the atomizing fluid, not only are acceptable burner tip temperatures produced, but also the resulting flame temperature is reduced thus producing an overall reduction in NO.sub.x.